Thermoplastic resinous sheets or laminates having external thermoplastic surfaces, especially polycarbonate external surfaces, are well known and commercially available materials. Such laminates or sheets can be engineered to possess a wide variety of chemical and physical properties. In many instances, items manufactured from these laminates or sheets are more break resistant at a lighter weight than glass and thus are used as a substitute for glass, as for example, in the manufacture of taillights, protective shields for street lights, safety shields in inspection windows, windshields, windows, and the like. However, though there are many advantages in the use of thermoplastic resins, glass remains far superior to such materials in the surface characteristics of mar and chemical solvent resistance.
In one line of development, the problems inherent to these poor surface characteristics have been remedied by incorporating thermoplastic laminae into a laminate with external laminae of glass. Such laminates benefit from both the mar resistance and strength of glass as well as the toughness of thermoplastic.
U.K. Pat. No. 2015427 discloses an in situ UV cure of the adhesive interlayer in glass-thermoplastic laminates. Such laminates as disclosed contain a substantial portion of their bulk in glass, thereby depriving the laminates to some degree of qualities of light weight and toughness which purely resinous laminates possess.
U.S. Pat. No. 3,666,614 discloses a laminate having a central lamina of polycarbonate and external laminae of glass bonded through adhesive interlayers such as polyvinylbutyral and the like. As above, these laminates contain a substantial portion of their bulk as glass and therefore become proportionately heavier and less shock resistant.
In another line of development, the poor surface characteristics of thermoplastic laminates and sheets have been improved by use of thin protective layers of various organic and inorganic coatings. These protective coatings have substantially improved the mar and chemical solvent resistance of many resinous materials, but further improvement is still necessary.
U.S. Pat. No. 4,200,681 which is assigned to the same assignee as the present invention discloses a polycarbonate article having deposited on the surface thereof (i) an intermediate primer layer containing the photoreaction products of certain polyfunctional UV cured acrylic monomers; and (ii) a top layer of vapor deposited silicon dioxide. This article, while an improvement over the prior art, suffers from a degree of erratic adhesion and crack resistance in the vapor deposited silicon dioxide coat.
Thus, while thermoplastic laminates and sheets exist which have relatively good or excellent surface characteristics of mar and chemical solvent resistance, such laminates or sheets suffer from either the increased bulk of external glass laminae or the reduced mar and chemical solvent resistance of thin protective coatings.
Therefore, it is an object of the present invention to provide mar and chemical solvent resistant thermoplastic sheets or laminates, which thermoplastic sheets or laminates have adhered to at least one surface thereof a thin sheet of glass bonded by a UV cured adhesive.
It is yet another object of the present invention to provide mar and chemical solvent resistant polycarbonate sheets or laminates, which polycarbonate sheets or laminates have adhered to at least one surface a thin sheet of glass bonded by a UV cured acrylated urethane interlayer or UV cured epoxy.